<!DOCTYPE html>
<body>
<div style="width:100%; height:4em; overflow:scroll">
<div style="position:relative; left:90%; top:1000px; width:100%; font-family:system-ui; font-size:16px">
Font-size in the validation bubble should be same as this paragraph.<input type=checkbox required>
</div>
</div>
<script>
document.querySelector('input').reportValidity();
</script>
</body>
